CXCR2 inhibition leads to inhibition in primary AML/MDS samples and increased survival in vivo. (A) Four primary MDS/AML samples were grown in the presence and absence of the CXCR2 inhibitor and demonstrated inhibition of leukemic colony growth after treatment. (B) The size of leukemic colonies was also reduced. NSG mice were xenografted with U937 cells containing control or CXCR2 shRNAs. (C) Mice with CXCR2 shRNA xenografts demonstrated significantly improved overall survival (log rank, P = .02).